Rotatable shafts can be coupled to gears or other shafts via a spline interface. The spline interface must be lubricated appropriately to prevent wear or galling due to fretting, vibratory loading, or other loading causing wear on the spline teeth. It is desirable to deliver enough lubrication to adequately protect the spline interface, but prevent excessive lubrication. Over lubrication requires additional pumping and storage capacity in the lubricant system, which increases system cost, creates weight penalties, and causes additional space claim requirements.
Dual splined shafts create additional challenges over single spline shafts. Because each spline must be lubricated, the splines must either have separate lubrication delivery systems or a single system must be able to deliver adequate lubrication to both ends of the shaft. Dual lubrication systems are expensive due to the redundancy and single systems tend to either over or under lubricate at least one of the splines.
One method of single source lubrication is to provide an opening in the wall of a partially hollow shaft and spray lubricating fluid toward the opening. One drawback to this type of system is that a significant amount of the lubrication will not pass through the opening because the shaft is rotating. The bigger the opening the more likely the lubricant will enter the hollow shaft, but the large opening makes it more likely that the lubricant will exit back out of the hollow shaft before moving to lubricate either of the splines. Furthermore the size of the opening is limited by the geometry of the shaft and the associated mechanical stress induced in a load bearing wall because of the large opening. If the opening is too small more lubricant is “wasted” as it hits the outer wall of the shaft and fails to enter through the opening as the shaft rotates. The present inventions provide novel and non-obvious, innovation needed in this field of technology.